It has been previously known to use prefabricated concrete panels to construct concrete wall systems for use in highway noise walls, retaining walls and other similar applications. An example of such wall systems is illustrated in U.S. Pat. No. 4,290,246 ('246) issued Sep. 1981.
Such walls have been manufactured by using rectangular steel casting forms positioned on a flat concrete casting slab. Wet concrete is poured into the casting forms. When the concrete hardens, the forms are removed, leaving finished rectangular concrete panels. The panels can then be assembled into a multipanel wall as shown, for example, in the '246 patent.
Such panels can be readily formed with a pattern on one side by employing so-called "form liners", which are rubbery semi-rigid sheets into which the desired pattern has been molded. These form liners are laid in the bottoms of the rectangular casting forms, and wet concrete poured into the forms on top of the form liners. Upon hardening, the bottom sides of the concrete panels conform to the pattern of the form liners. In some applications (such as those requiring patterns on both sides of the panels), it is desired to form a pattern on the topsides of the panels.
Where the pattern desired on the topside consists of vertical grooves, a rolling pin arrangement may be satisfactory. For example, in one arrangement, the rolling pin consists of a cylindrical 3-inch diameter stainless steel shaft with multiple stainless steel discs mounted on the shaft with setscrews. For an eight-foot wide casting form, the shaft of the rolling pin is 9 or 91/2 feet long. The operator rests the ends of the rolling pin shaft on the sidewalls of the form, and then rolls the pin across the surface of the wet concrete to form vertical grooves. The difference in diameters of the shaft and discs thus govern the groove depths. The disc widths and cross section are governed by the width and cross sections of the discs; and the groove spacing is governed by the spacing of the discs on the cylinder shaft.
While the rolling pin system may be satisfactory for patterns with shallow grooves, it has proven unsatisfactory where relatively deep grooves (e.g. 11/2 inches deep) are required. In such applications, if the roller is used while the concrete is very wet, the wet concrete flows back into the grooves. Alternatively, if the roller is applied later, after the wet concrete partially hardens, the roller does not cut deep enough into the concrete surface. Multiple passes at different stages do not solve the problem.